Projection lens with add lens elements

ABSTRACT

A projection lens for operation between fixed conjugates includes a pair of add lenses for selective combination with the basic lens for changing the magnification of the system. The basic lens operates at unity magnification, with one add lens at 0.74X and with the other add lens at 0.65X magnifications.

OR 1-2221522. i 3 2V United State. [111 ,817,599

5 McCrobie 71,, 76 1 June 18, 1974 1 PROJECTION LENS WITH ADD LENS 2,975,674 3/1961 Tibbetts et a1 350/183 3,363,964 H1968 Macher 350/183 ELEMENTS A projection lens for operation between fixed conjugates includes a pair of add lenses for selective combination with the basic lens for changing the magnification of the system. The basic lens operates at unity magnification, with one add lens at 0.74X and with 4 Clains, 3 Drawing Figures [75] inventor: George L. McCrobie, Upland, Calif.

A 1 x C f St f d Primary Examiner-Ronald L. Wibert [73] ssgnee 3 orpora Ion am or Assistant Examiner-Conrad Clark [22] Filed: Mar. 21, 1973 [21] Appl. No.: 343,331 [57] ABSTRACT [52] US. Cl 350/183, 350/215, 350/216, 350/222 [51] Int. Cl. G021) 15/02 [58] Field ,of Search 350/183, 215, 216, 222

[56] References Cited the other add lens at 0.65X magnifications.

UNITED STATES PATENTS 1,553.211 9/1925 Barr et al 350/183 I II In 1! I/ 4 e a 4 A "1 f2 "4 "a "r "a fie s 0/ 0 slal'rlsas PATENTEDJun I 8 m4 FIG 1 PROJECTION LENS WITH ADD LENS ELEMENTS BACKGROUND OF THE INVENTION This invention relates to a projection lens and in particular to a projection lens for operation between fixed conjugates in which additional lenses are selectively placed in combination for the purpose of changing magnification.

Copying machines are often required to produce copies of an original document or other object that are either enlarged or reduced in size. For the sake of economy in machine design, the overall conjugate length or optical axis is preferably fixed and the lens system is manipulated to obtain the desired magnifications. An example of the type of optical system referred to is disclosed in US. Pat. No. 3,741,62l, issued June 26, l973, to George L. McCrobie. In this patent, an add lens projection system is disclosed in which a basic projection lens group is disposed along an optical axis at a first position to provide a 1:1 magnification. A pair of add lens elements is provided which are selectively and alternatively positioned in the optical axis and the entire lens moved to various positions therealong to provide varying magnifications of the projected image. The present invention is a modification of the basic concept disclosed and claimed in US. Pat. No. 3,741,621.

It is an object'of the present invention to provide a multi-focal projection lens for use between fixed conjugates and which is well corrected for chrometic aberrations, spherical aberration, coma, and astigmatism and which has a substantially flat imagefield.

DRAWING FIG. 1 is an optical diagram of the basic lens group according to the present invention;

FIG. 2 is an optical diagram of the lens shown in FIG. I with a first add lens to provide a desired magnification;

FIG. 3 is an optical diagram ofthe lens shown in FIG. I with a second add lens to provide a different magnification.

DESCRIPTION Referring now to FIG. 1, a copy lens or projection lens is generally indicated at 2. It includes the followin elements disposed in optical alignment:

A front doublet 4, a single lens 6, a single lens 8, and a doublet l0. Lens 2 is disposed between conjugate object and image planes l2 and 14 respectively.

Doublet 4 includes a convex-piano lens element l and a piano-concave lens element ll, together forming a convex-concave doublet. Lens 6 is a convex-concave lens, also designated lll. Lens 8 is a concave-convex lens, also designated IV. Doublet 10 includes a concave-piano lens element V and a plane-convex lens element VI, together forming a concave-convex doublet.

In FIG. 2, a single add lens 16 is positioned between I the lens 2 and the image plane 14. Add lens 16 is a conwhich includes a concave-plano lens element VIII and a plano-convex lens element IX, separated by a small air gap. As with add lens 16, add lens 18 is suitably mounted for movement into and out of optical alignment with lens 2 as desired.

The basic lens 2, shown in FIG. I, and made according to the following specification, provides a magnification ratio of l:l.0l. In the arrangement of FIG. 2, lens 2 with add lens 16 provides a magnification of l:0.74 In the arrangement of FIG. 3, lens 2 with add lens 18 provides a magnification of 1:0.65.

The parameters of the lens elements which make up the above described lens are as listed in the following table in which N,, is the refractive index for the D line of sodium, and is the Abbe number. Radii (R), thicknesses (T), and spacings (S), are expressed in inches and a negative sign indicates radii on centers of curvature lying on the object side of their vertices.

2. A lens as defined in claim I and further including an add lens according to the following specification:

Thick- Lcns Radius ness Space Refractive Abbe (R) (T) (5) Index (ND) Number (v) 3. A lens as defined in claim 1 and further including an add lens according to the following specification:

Thick- Lens Radius ness Space Refractive Abbe (R) (T) (5) Index (ND) Number (v) r S =0.580 R e-62.0090 VIII T,.=0.350 ND, =I.6I644 Vds=36.63

R =pIano S,-,=0.020 R =plano IX T,=0.38O ND =I.5I I05 V419=60.4I

4. A multi-focal lens including:

b. a first add lens according to the following specification:

Thick- Lens Radius ness Space Refractive Abbe (R) (T) (5) Index (ND) Number (1') S,=0.580 R ,=39.3520 7 VII 'I =0.360 ND =L5I673 IM7=64.I7

c. a second add lens according to the following specification:

Thick- Lens Radius ness Space Refractive Abbe (R) (T) (8) Index (ND) Number S.=0.580 R,,=62.0090 VIII T,.=O.350 ND..=I.6I644 u =36.63

R =plano S,= 0.020 R =plano IX T,==0.380 ND,,=I.5I I05 l/d9=60.4I

said first and second add lenses being selectively disposable in optical alignment with said basic lens group to vary the magnification of said lens. 

1. A lens according to the following specification: Thick- Lens Radius ness Space Refractive Abbe (R) (T) (S) Index (ND) Number ( Nu ) R1 3.5034 I T1 0.754 ND1 1.63844 Nu d1 55.42 R2 plano II T2 0.724 ND2 1.57297 Nu d2 42.58 R3 2.5624 S1 0.321 R4 4.0028 III T3 0.516 ND3 1.64316 Nu d3 47.96 R5 6.1720 S2 0.954 R6 -6.1720 IV T4 0.516 ND4 1.64316 Nu d4 47.96 R7 4.0028 S3 0.321 R8 -2.5624 V T5 0.724 ND5 1.57297 Nu d5 42.58 R9 plano VI T6 0.754 ND6 1.63844 Nu d6 55.42 R10 -3.5034
 2. A lens as defined in claim 1 and further including an add lens according to the following specification: Thick- Lens Radius ness Space Refractive Abbe (R) (T) (S) Index (ND) Number ( Nu ) S4 0.580 R11 -39.3520 VII T7 0.360 ND7 1.51673 Nu d7 64.17 R12 -32.7860
 3. A lens as defined in claim 1 and further including an add lens according to the following specification: Thick- Lens Radius ness Space Refractive Abbe (R) (T) (S) Index (ND) Number ( Nu ) S4 0.580 R13 -62.0090 VIII T8 0.350 ND8 1.61644 Nu d8 36.63 R14 plano S5 0.020 R15 plano IX T9 0.380 ND9 1.51105 Nu d9 60.41 R16 -33.3440
 4. A multi-focal lens including: a. a basic lens group according to the following specification: Thick- Lens Radius ness Space Refractive Abbe (R) (T) (S) Index (ND) Number ( Nu ) R1 3.5034 I T1 0.754 ND1 1.63844 Nu d1 55.42 R2 plano II T2 0.724 ND2 1.57297 Nu d2 42.58 R3 2.5624 S1 0.321 R4 4.0028 III T3 0.516 ND3 1.64316 Nu d3 47.96 R5 6.1720 S2 0.954 R6 -6.1720 IV T4 0.516 ND4 1.64316 Nu d4 47.96 R7 -4.0028 S3 0.321 R8 -2.5624 V T5 0.724 ND5 1.57297 Nu d5 42.58 R9 plano VI T6 0.754 ND6 1.63844 Nu d6 55.42 R10 -3.5034 b. a first add lens according to the following specification: Thick- Lens Radius ness Space Refractive Abbe (R) (T) (S) Index (ND) Number ( Nu ) S4 0.580 R11 -39.3520 VII T7 0.360 ND7 1.51673 Nu d7 64.17 R12 -32.7860 c. a second add lens according to the following specification: Thick- Lens Radius ness Space Refractive Abbe (R) (T) (S) Index (ND) Number ( Nu ) S4 0.580 R13 -62.0090 VIII T8 0.350 ND8 1.61644 Nu d8 36.63 R14 plano S5 0.020 R15 plano IX T9 0.380 ND9 1.51105 Nu d9 60.41 R16 -34.3440 said first and second add lenses being selectively disposable in optical alignment with said basic lens group to vary the magnification of said lens. 